1. Field of the Invention
The present invention relates to an apparatus and method for encoding a Low Density Parity Check (LDPC) code using a message passing algorithm; and, more particularly, to an apparatus and method for encoding an LDPC code which can reduce hardware complexity of a complicated encoding apparatus and perform encoding at high-speed by designating a predetermined parity bit and calculating a check node value and a parity bit using a message passing algorithm where offset of an LDPC code decoding procedure is applied.
This work was supported by the IT R&D program for MIC/IITA [2006-S-002-02, “IMT-Advanced Radio Transmission Technology with Low Mobility”].
2. Description of Related Art
There are some cases that a signal transmitted in a digital format cannot be demodulated in a receiving end according to the state of a channel in a wired/wireless communication system. These cases are caused by an error incident rate increasing due to a high-speed wired/wireless communication. Diverse techniques are applied to reduce the error incident rate and a channel coding technique is representatively applied.
Recently, the channel coding technique is applied to most wireless communication systems. In particular, a Low Density Parity Check (LDPC) code has a great attention from people as a next generation channel codec in the wireless communication system.
First of all, it is assumed that the LDPC code is encoded according to a systematic method. That is, the systematic method means that a part of a packet is output in the same format as an input bit. Also, a rest part of the packet has a format that additional information corresponding to the parity bit is sequentially added. Accordingly, when the input bit is completely input in a block in charge of encoding function, encoding is performed. A rate that the parity bit takes in the entire packet is differed according to a code rate. Accordingly, the code rate is fixed by an H matrix.
Meanwhile, there is an LDPC code encoding method suggested by “Richardson” as a related art of the LDPC code encoding method. The related art includes the steps of segmenting the H matrix, dividing the H matrix into sub matrixes, and creating an output parity bit when an input vector of simultaneous equations of the matrix is given.
An LDPC code encoding method simpler than the LDPC code encoding method suggested by “Richardson” is suggested by “Motorola Inc.” in “Institute of Electrical and Electronics Engineers (IEEE) 802.16e”. In the LDPC code encoding method, the matrix is not operated but the LDPC code is encoded by directly acquiring a parity bit through simultaneous equations.
The LDPC code encoding method has problems that it is difficult to process a signal at high-speed due to an operation of dividing a sub-matrix. Also, the LDPC code encoding method of “Motorola Inc.” has a problem that encoding complexity increases by directly acquiring the parity bit and the hardware resource load remarkably increases.
There is another conventional LDPC code encoding method for organizing an H matrix and encoding a new LDPC code based on the reorganized H matrix. This conventional encoding method defines and encodes the new H matrix by largely changing the conventional H matrix. That is, the parity check matrix is newly defined but a structure is not a generalized conventional dual diagonal structure.
This conventional encoding method can create a new code by performing encoding based on the new H matrix. However, this conventional encoding method has a problem that a complex matrix operation should be performed.